Extraction of lubricating oils



Patented Sept. 1, 1936 UNITED STATES EXTRACTION OF LUBRICATING OILS Ogden Fitz Simons and Frank Cutshaw Croxton, Hammond, Ind., assignors to Standard Oil Company,

Chicago, Indiana 111., a corporation of No Drawing. Application June 2, 1934, Serial No. 728,674

3 Claims.

This invention relates to the fractionation of lubricating oil stocks by the use of certain new and improved solvents.

The solvent fractionation of lubricating oil stocks by the use of selective solvents is known to the art, and our invention is an improvement therein which comprises the use of a solvent mixture of sulfur dioxide and one or more liquefied normally gaseous olefinic hydrocarbons such as ethylene, propylene, butylene and the amylenes.

The composition of our new solvent can vary within wide limits, say from 95% sulfur dioxide and 5% olefinic hydrocarbon or hydrocarbons to 80% olefinic hydrocarbon or hydrocarbons and 20% sulfur dioxide. Other solvents can also be present in the mixture. The results accomplished are highly superior to those obtained by the use of sulfur dioxide alone since the latter is too highly selective and does not remove a suificiently high proportion of extract material.

Our new solvent can be used in any of the known solvent extraction processes. Thus, for instance, it can be used by heating the lubricating oil stock and the liquefied solvent under pressure to a temperature above the complete miscibility temperature and then cooling the system to separate two liquid phases, separating these phases and recovering the solvents from both ex- 30 tract and rafllnate by distillation for re-use. Our

solvent has the advantage that both components of it can be removed readily from the lubricating oil components without fractionation of the solvent and without the use of high grade heat.

Alternately our new solvent can be used below themiscibility temperature by merely agitating it with the stock and separating two liquid phases. Several such steps can be used in sequence in a batch countercurrent system of any 40 of the types known to the art. Similarly our solvent can be used in any of the known types of continuous countercurrent systems, for instance by introducing the stock near the bottom of a tower, introducing the liquefied solvent near the top of the tower, removing an extract phase from the bottom of the tower and removing a railinate phase from the top of the tower. In either type of countercurrent system the two components of our new solvent can be introduced at difierent points in the system.

Another desirable process utilizing our new solvent comprises adding one or more liquefied normally gaseous olefinic hydrocarbons to a wax bearing lubricating oil stock, cooling to precipi- 55v tate the wax, the cooling preferably being accomplished, at least in part, by evaporating a portion, but less than all, of the olefinic hydrocarbon or hydrocarbons, removing the precipitated wax,

adding sulfur dioxide to the dewaxed solution and solvent extracting by any of the aforementioned methods. The dewaxing step may suitably be accomplished by methods analogous to those of Giles Patent 1,943,236.

As an example of my process a wax-bearing lubricating oil distillate from a Mid-Continent crude oil can be diluted with about four times its volume of liquefied commercial propylene, cooled to about 40 F., at least partly by evaporation of a portion of the propylene, and dewaxed at about the temperature mentioned, the dewaxed solution can then be agitated with a volume of liquefied sulfur dioxide about equal to the volume of propylene remaining in the solution. This results in the formation of two liquid phases, an extract phase and a raflinate phase. These can then be separated and solvent can be removed from each of them, for instance by flash or vacuum distillation.

While we have described our process in connection with certain specific embodiments thereof we do not mean to be limited thereby but only by the broadest valid interpretation of the appended claims.

We claim:

1. A process for the solvent fractionation of a lubricating oil stock which comprises mixing said stock with a solvent consisting of from about 20% to about 95% of liquefied sulfur dioxide and from about 5% to about 80% of at least one liquefied olefinic hydrocarbon having from two to five carbon atoms per molecule and separately recovering an extract fraction and a raffinate fraction.

2. A process according to claim 1 in which prior to the steps recited in claim 1 the lubricating oil stock has been dewaxed in the presence of at least one of said olefinic hydrocarbons, at least a substantial part of said olefinic hydrocarbon remaining in the dewaxed solution and forming at least a substantial part of the olefinic hydrocarbon utilized in the steps recited in claim 1.

3. A process according to claim 1 in which prior to the steps recited in claim 1 the lubricating oil stock has been dewaxed in the presence of at least one of said olefinic hydrocarbons, a substantial part of said olefinic hydrocarbon being evaporated to accomplish at least a part of the chilling required by the dewaxing operation and at least a substantial part of said olefinic hydrocarbon remaining in the dewaxed solution and forming at least a substantial part of the olefinic hydrocarbon utilized in the steps recited in claim 1.

OGDEN FITZ SIMONS. FRANK CUTSHAW CROXTON. 

